Blasting cartridge



Nov. 3, 1931. R. w. DULL sLAsTINo CARTRIDGE ...1.... ml Il Illu H J A Patented Nov. 3, 1931' UNITED STATKIS .PATENT f OFFICE RAYMOND W. DULL, OF LA GRANGE,

PANY, OF CHICAGO,

BLAST-ING CARTRIDGE Application tiled September 16, 1929. Serial No. 392,849.

This invention relates to blasting cartridges of the general type shown in the Ferrell et al. Patent No. 1,610,274, granted December 14, 1926. As shown in the patent, this type of cartrid e consists of a substantially c lindrical stee shell having an internal gas c amber, a pressure responsive discharge device associated with one end of the shell and charging and energizing means -associated with the other end of the shell.y The'energizing means is in the form of an electrode which.

extends thru a wall of the shell and into the gas chamber. The electrode forms one terminal of a circuit including an electrically activated heat producing device, as an intermediate element, and the steel shell, as the other electrode or terminal. The function of the electrode requires that it be reliably insulated from the shell and the fact that it en ters the gas chamber requires that it be well packed to prevent leakage of gas and withstand pressure.

Since the advent the above mentioned patent, cartridge structures have been develo ed and much of this development work has en directed to improvement of the mounting, insulation and packing of the electrode. Notwithstanding these efforts, this portion of the cartridge has continued to be a source of trouble. The dificulties involved can be of the cartridge shown in many improved readily appreciated in view of the fact that' the electrode is subjected to whatever pressure exists within the gas chamber and that such pressure approximates 40,000 pounds r square inch at the time of discharge. The eiect of this extremel high pressure has been to blow out or, at least, rupture the insulating pac g to such an extent as to destroy the gas tight seal between the electrode and shell.

An object of the present invention is to provide a remedy for these defects.

Specifically, it is an object of the invention to provide an insulated andsealed electrode for blasting cartridges of the type indicated, of such construction and design that the ratio of ressure area to preure resistin area wllfprovide a substantial factor of saety.

' whereby A tion with what may The more specific objects of the invention will appear in connection'with the following description of the accompanying In the drawings, A

Figure 1 is a view in side elevation with a portion of the wall Lbroken away' to disclose the position of the heater `in a cartridge of the type under consideration,

Figure 2 is a view in longitudinal section of a cartridge embodying my invention,

Figure 3 is a view in taken along line 3-3 of Figure 2', y

Figure 4 is a view in transverse section taken along line 4-4 of Figure 2, and

Figure 5 is a transverse sectional view taken along line 5-5 of Figure 2.

The improvements constituting the present invention are embodied in a cartridge which in general` comprises a substantially cylindrical metallic body 1, having an internal gas chamber 2, the open end of which is adapted to be closed and sealed by means of a rupturable disc 3. This disc seats against a shoulder 4 .formed on the body and is backed up by a relatively hard steel shear ring 5. The disc and shear ring are heldin assembled relation with respect to the cartridge body by means of the tubular portion 6 of a discharge cap 7. The portion 6 is externally threaded and engages corresponding threads formed internally of the discharge end of the cartridge. The discharge cap is provided with an axial gas passage 8 and a plurality of transverse or radially arranged outlet ports 9. The opposite end of the cartridge is provided lwith an elec- 'trode 10 which extends into the gas chamber 2 and which is eiectively sealed and insulated with respect to the cartridge body. A valve 11 cooperates with the outer end of the electrode 10 to control the passage of gas therethrough and into the chamber. A terminal cap 12 associated with the extreme end of the cartridge body rovides means a source of electricity may be connected to the electrode and metallic cartridge bog'yl respectively.

v e improvements with which the present invention is chiefly concerned are in connecbe termed the charging transverse section, n

drawings. L

- the discharge end thereof. One of the principal features is the construction and mounting of the electrode 10 in the end of the shell body. It might be stated in this connection that the function of the electrode is to make contact with one end of an electrically energizable heater unit 13, the opposite end of which is adapted to contact with some portion of the metallic cartridge body or some element having electrical contact therewith,

such, for example, as the rupturable disc 3.-

The electrode 10 passes through an aperture in the end wall 14 of the gas chamber 2. Inwardly of the wall 14 there is provided a substantially cylindrical pocket 15 and on the opposite side of the wall the shell body is extended in sleeve-like form to provide an internal pocket substantially circular in cross section. A flange 17 is formed on the electrode and this flange is disposed within the cylindrical pocket 15. Insulating members 18 and 19 serve to separate the electrode from the metallic shell body in order to prevent the passage of electricity directly from one to the other. The inner end of the electrode is surrounded by an insulating sleeve 20 which serves to separate the electrode from the surrounding nut 21 which has electrical connection with the cartridge body. The head of nut 21 is of heXagon or other suitable form adapted to receive, a socket wrench or the like and the periphery of the nut is provided with screw threads for cooperation with corresponding threads formed internally of the ocket 15. By virtue of this construction, At e nut may be ad-` justed to provide the necessary pressure betwe n the adjacent surfaces of the Bange 17, wall 14 and interposed insulating member to provide effective seal against the escape of gas from the chamber 2. This nut, by virtue of its position and relation to the electrode performs anadditional and very important function in the cartridge. It will be observed that the entire cross sectional area of the nut is exposed to the interior of the gas chamber, but, by'reason of the connection between the nut and the body of the shell, whatever pressure is' exerted on the nut is transmitted directly to the shell body and is not imposed upon the electrode and the material employed to ,insulate the electrode from the body. This arrangement gives rise to the possibility of making the inner end of the electrode of comparatlvely small cross sectional area as compared with the area of the surfaces of flange 17 and wall 14 which provide the gas tight seal for the electrode. In the specific construction shown, the cross sectional area of the inner end of the electrode which is exposed to the pressure within the gas chamber is substantially equal to, or less than the area of the sealing surfaces and in this relationship lies the solution to the problem of providin an effective and durable seal for the e cctrode. If this relationship is not employed, it is practically impossible to lind an insulating material capable of withstanding the pressures involved in a cartridge of this character.

An axial passage 23 extends from the outer end of the electrode to a point adjacent the inner end thereof at which point a transverse passage 24 is located to place passage 23 in communication with the interior of the gas chamber. The valve body 25 which carries valve member 11 is screw threaded on the outer end of the electrode and is insulated 'from the cartridge body by means of an insulating disc 27. A charging port 26 in the valve body communicates with the interior thereof and with the end of passage 23 when the valve member 11 is adjusted out of engagement with the end of the electrode.k

The terminal cap 12is adapted to be detachably connected with the end of the cartridge body by means of suitable lugs and bayonet slots as indicated at 27 and 28. Metallic plug 29 is centrally positioned in the terminal cap and is insulated therefrom by the disc 30 and sleeve 31. A setscrew 32 is provided for the pur ose of securing a conductor in thev plug. may be secured in the terminal cap by means of theaperture 33 and setscrew 34. Electrical contact is established between the plug 29 and the electrode by means of a coil spring 35 having one end engaging the plug and the op osite end engaging the valve body.

or the purpose of rendering the cartridge normally inoperative a short circuiting device is provided for establishing an electrical connection between the electrode and the shell body. This device consists of a sleeve member 36 having an inwardly directed flange 37 which is adapted to cooperate with a lurality of knife edge contacts 39 forme on the under surface of the valve body. A spring 38 is interposed between the flange 37 and the outer surface of the wall14. This spring tends to normally maintain the flange 37 in engagement with the contacts 39 and .since the spring is in electrical contact with the body of the cartridge, a short circuit is provided from the electrode to the body. The sleeve 36 is so designed as to length that it 'is adapted to be engaged'and moved by the end of the terminal cap 12 when the latter is attached to the cartridge, thus breaking the connection between flange 37 and contacts 39.

The extreme inner end of the electrode 10 is provided with external screw threads for second conductor 1 lill llU

to the pressure in tlie chamber is equal to or therein. Slots 43 are provided in the end of the support 41 to receive a suitabl formed wrench to be used in assembling t e heater support on the electrode.

The cartridge hereinabove described is adapted to be charged with a highly compressed or liquefied gas through the valve controlled passage in the electrode. The dis-` charge of the cartridge is effected by connecting the leads from a source of electricity to the electrode and cartridge body respectively, thereby includin the heater unit in circuit with-a source o electricity. When this circuit is energized, the heater unit gives oi a suilicient amount of heat to va orize`the charge within thecartridge an increase pressure thereof to a predetermined point at which the disc 3 is designed to rupture. The rupture of disc 3 permits the escape of the gaseous charge through passage 8 and f radial ports 9 of the discharge cap and into the material to be blasted.

Prior to thepresent invention considerable diiliculty has been experienced with a wide variety of structural forms of blasting cartridges, particularly in connection with the insulation and sealing of the electrode. At the time of discharge' of a cartridge of this type the pressure within the gas chamber approximates 40,000 pounds per square inch and this extremely high ressure has caused the destruction of the insulating elements between the electrode and cartridge body in many different types of construction. Ari

' entirely adequate solution of this diiicultyc seems to be present in the construction herein described wherein the electrode nut receives much o the pressure which exists within' the gas ch mber and transmits the same directly to the cartridge rather than to the electrode. It has been found that with such a construction it is ossible to maintain a reliable relationship etween the area of the electrode lwhich is subjected to 'pressure and the area of the insulating material which must resist this pressure. Satisfactory results can be secured if the end of the electrode exposed less than the area of the pressure resistingy surface, although in order to secure a desirable factor of safety, it is well to-provide a substantially greater area for the resistin surface than exists for the surface expose to the pressure.

Claims:

1. In a device of the character described, the combination with a body having a gas chamber, of an electrode projectingM thru the body and extending, into ysaid chamber, 'cooperating sealing surfaces on said electrode and body'and a material having the combined properties of an insulator and packing interposed between said surfaces, the effective area of said surfaces being substantially equal to or greater than the area vinte of the electrode which is exposed to 2. A blasting cartridge comp a me talli'c body having an internal gas amber, an electrode in rojecting thru an ope said body and) having a portion thereo e posed to the-pressure within said chamber, an insulating membgr inte between said electrode and the walls o said opening, cooperating sealin surfaces on said electro e an body, an ins ating and sealing member between said surfaces, the eiective area of the sealinglsurface on said ele'ctrode being substantia y equal to or greater than the area of the ortion expod to the pressure within the c amber.

3. A blasting cartridge comprisin a metallic body having an internal gas c amber, an electrode ro3ecting thru an opening in said body and) having a portion thereof exposed to the pressure within said chamber, coo rating pressure resistin surfaces on sai electrode and body, the e ective area of said ressure resist' surfaces being at least equaFto the area of t at surface of theielectrode which is exposed to the pressure within the chamber.

4. A blasting cartridge comp a metallic body having an internal gas c amber,

`said body having a circular opening thru a wall thereof and a cylindrica pocket ad- 'acent said opening on the interior of said dy and communicatin with said chamber an electrode positioned in said opening and extending on radial flan within sai on said electrode and disposed pocket, an insulat' and sealing member interposed betweent e end wall of said pocket and one face of said flange, and means surrounding said electrode and actin against the other face of said flange for eectingsthe sealed relation, said means serving to prevent access of pressure within the chamber to the inner radial fa'ce of said flange.

5. A blasting cartridge comprising a metallic body having an internal gas chamber, said body having a circular opening thru a wall thereof and a cylindrical pocket ad- 'a'cent said openin on the interior of said dy and communicating with said chamber an electrode positioned in said enin an` extending on opposite sides of sai w an insulatin sleeve ositioned between said electrode an the wa lof said circular opening a ra'dial flan on said electrode disposed within said poc et, an insulati member interposed between the end wa of said opposite sides of said wall, a

iis

4 K remesa for c? eiration with tle threads on said mint.

6. astmg' cartri ge comprising a su stantially cylindrical metalli'crbody having a gas chamber formed therein, a pressure 5 responsive discharge device associated with one end of said body and gas chamber, a

transverse wall adjacent the opposite end of said body said wall havin a perforation therethru leading into the c amber, an electrode extending thru said perforation and into the chamber, a radial ian e formed intermediate the ends of said e ectrode, said flan e being positioned within the chamber and aving a radial surface adapted for cooperation with the inner radial surface of said transverse wall to provide a seal, a nut surrounding the inner end of said electrode and adapted to coact with the otherl radial face of said fi e, said nut having threaded engagement wit the interior of said body whereby axial movement of the electrode may be eie'cted, and insulating material interposed between adjacent surfaces of the electrode and the body and nut tively.

26 Signed at Chicago, Ill., this lt day of September, 1929.

RAYMOND W. DULL. 

